Diaphragm compressor



Jan. 31, 1933. yv, R, B RQWN 1,895,602

DIAPHRAGM COMPRES S 0R Filed May l2, 1932 wel:

n v 'IH Patented Jan. 31, 1933 PATENT OFFICE WILLAI B. BROWN, F CHICAGO, ILLINOIS DIAPHRAGM COMPRESSOR Animation nea nay 12, 1932. semi no. 610,903.

This invention relates to compressors and particularly to diaphragm air compressors suitable for use with spray guns and the like.

The main objects o this invention are to provide an im roved dia hra compressor in which the diaphragm unctions as acrosshead and is easily replaceable; to provide an improved compressor having a simple onepiece crank case and improved means to shield the diaphragm from the crank case oil; to provide an improved compressor having an integrally formed piston and connecting rod; to provide a compressor having a single crank case casting embodying integral shaft bearin s, oil reservoir, diaphragm shielding oil aiiies and diaphragm holding means; to provide a'compressor having a piston connecting rod journaled on an eccentric driving cam; and to provide a compressor having a sin le head casting comprisin a plenum chamer, intake port and chec valves.

A specific embodiment of this invention is shown in the accompanying drawing in which:

Figure 1 is a cross sectional view taken transversely of the drive shaft.

Fig. 2 is a sectional view taken parallel to the drive shaft.

Fig. 3 is a cross sectional view taken on the line 3-3 of Fig. 1.

In the form shown, my improved compressor comprises a one-piece crank case casting 1 having outwardly flared walls 2 forming a iston chamber3 and terminatlng in an annu ar iianged rim 4; a single casting compressor head 5 comprising a plenum chamber 6, an intake port 7 and an annular flange 8 adapted to engage the flange 4; a drive shaft 9 extending into the crank case and carrying therein an eccentric cam10; a connecting rod 11 journaled on the eccentric cam 10 and carrying an integrally formed piston head 12; and a diaphragm 13 clamped between the fianges 4 and 8 and secure to the piston head 12.

The walls of the crank case casting 1 are contracted abovel the crank portion 14 to form an upwardly extending neck 15 which houses the connecting rod 11 and extends beyond the junction with the fiared walls 2 to terminate in an annular upstanding liange or collar 16, the rim of the flange 16 being positioned somewhat below thelevel of the W annular angefi. The inner margin oi' the 53 flange 4 is provided with an annular groove 17 to set off a rib 18 which serves as a bearing surface against which' the diaphra 13 is clamped by the compressor head 5. air of feet 19 are integrally formed on the ot- 6C tom portion of the casting 1, and a sediment well or trap 2O is also provided. rlhe trap 20 is drilled and tapped and a plug 21 is inserted in the hole to provide a means `.tor draining ofi the crank case oil. 65 At each side of the crank case through which the shaft 9 extends, shaft bearings 22 and 23 are integrally formed on the castingi 1. These bearings are drilled and finished and the shaft 9 is journaled therein without 70 the use of separate lining materials, the oil from within the crank case serving to keep them lubricated. The crank case castin is also tapped below the bearing 23 an a ycapped or plugged elbow 24 is inserted to 75 provide a filling means for the oil reservoir. The compressor head 5 is in the form of a hollow box-like casting having a substantially concave bottom 25 and a plurality of integrally formed external radial lins'26. rThe B@ intakeport 7 opens at the top of the head 5 and is bounded by partition walls 27 which divide it from the plenum chamber 6. The bottom 25 of the head is provided with a pair of threaded apertures 28 and 29 which lead 85 into the intake port 7,- and the plenum chainber 6 respectively, and a check valve 30, and an oppositely disposed check valve 31 are threaded into the respective apertures.

The checkvalve 30 is arranged so as to be W normally open and the valve 31 is arranged to be normally closed. Each valve consists of an externally threaded cup-like casing havin a slot 32 across its closed end and a centr aperture 33 therethrough. A disk 34, of bake- 95 like or the like, of larger diameter than the aperture 33 but smaller than the inside diameter of the casing, is inserted within the casing and is held therein by a double bent wire 35 which is sprung into a groove on the inner `00 side of the casing, the disk retaining wirebeing spaced from the disk to allow restricted vertical movement of the same.

The compressor head 5 is provided with a threaded hole 36 at its top and an outlet pipe 37 is screwed therein. VAlso an annular rib 38 is provided at the innermargin of the flange 8 to coact with the bearing surface 18 on the crank case casting. The head 5 is secured to the crank case'zeby means of a plurality of cap screws 39`inserted through holes in the flange 8 and engaging tapped complementary holes in the flange 4.

The piston head 12, which is integrally formed with the connecting rod 11, is provided with a flat top and is of lesser diameter than the piston chamber 3. A marginal dependinglannular skirt or flange 40 of larger diameter than the langeor neck 16, is formed on the head 12 and extends downwardly to surround and overlap the flange 16. The flange 40 is spaced from the flange 16 and is of such a length that it will overlap the flange 16 during' the entire stroke of the piston 12. A second flange or skirt 41 spaced from the flange 40 and surrounding the same concentrically is provided on the piston head 12 and serves as a supplementary baille.

The overlapping flanges 16 and 40.I and the flange 41, provide a system of baflles that effectively precludes the splashing of oil from the crank case onto the diaphragm 13 and a drain hole 42. at the base of the flange 16. per mits the oil intercepted by the baffles 40 and 41 to drain back into. the crank case oil res er Voir.

The diaphragm 13 is securely clamped between the coacting ribs 38 and 18 on the compresser head 5 and the crank case 1 respectively and is 'fastened to the piston head 12 by means of a broad plate 43 which in turn is fastened by the screw 44 threaded into the connecting rod 11 and countersunk into the plate 43. The concave bottom 2.5 of the com- -presor head provides a space to receive the plate 43 on the upward stroke of the piston and a breather hole 45 is provided in the side walls 2. To assemble my improved compressor. the eccentric cam 1G is first inserted in the end of the connecting rod 11. and the assembly is passed through the neck 15 so that the cani 10 will be disposed in the crank shaft. chamber 14. The shaft 9 is then passed through the bearing 22, and ofl-center hole in the eccentric cam 10, and into the bearing 23, and the eccentric cam is secured to the shaft with a set screw or other suitable means manipulated through the drain hole in the sediment pocket 20 from which the plug 21 has been removed.

The eccentric cam 10, after being secured to the shaft 9 serves as a thrust collar acting against the inner sides of the crank case" to receive thrust in either direction longitudinally of the shaft 9.

The diaphragm 13 is then laid over the top `ol" the rrankcase 1 so that its edges overlap the annular bearing surface or rib 18. The plate 43 is laid on top ofthe diaphragm, and the screw or holt44 is inserted through the plate and diaphragm andthreaded into the connecting rod 11 to securely clamp the diaphragm against the top surface of the piston head 12. The compressor head 5 is then placed over the top of the crank case so that the ,holes for the bolts 39 are in registry and is clamped down by means of a bolt 39 passing through the coacting flanges 4 and 8. When the compressor head 5 is clamped against the crank case 1, the annular ridge 38 on the compressor head coacts with the bearing surfacep18 to securely clamp the diaphragm 13 therebetween and lock the same against possible displacement.

lu operation the crank case is rst filled with a medium motor oil through the elbow 24`until the oil has reached a predetermined level, preferably just-belowthe top of the elbow 24. The drive shaft -9is provided with a pulley, not shown. of proper size according to the speed of the driving motor, to provide a speed of approximately 1.000 R. P. M.; and a safety valve` and pressure regulator. not

shown` is installed in the outlet pipe 37, inv

order to maintain a constant pressure in the plenum chamber 6.

As the drive sha-ft 9 -is revolved the eccentric cam 10 causes the connecting rod and pistonhead to reciprocate, and the diaphragm 13 functions as a. crosshead to maintain a substantially linear motion of the piston head 12. On the downward stroke of the piston head, air is drawn through the intake port 7 and the check valve 30, into the space between the hottom`25 of the compressor head and the plate 43 of the piston head. On the upward stroke, the disk 34 in valve 30 is` forced upwardly to close the valve opening 33, and a similar disk in valve 31 is forced 4 upwardly and away from the opening 33 therein to permit the air to be forced into the plenum chamber 6. The air pressure in .the plenum chamber 6 and the vacuum created by the piston head on its downward stroke. serve to closethe check valve 31 when air is being drawn into the compressor.

As the eccentric 10 is revolved in the cra-nk .case chamber 14. the oil therein will be splashed considerably. and will tend to work its way up into the piston chamber 13. The upwardlyv extending collar or flange 16 functions to substantially prevent the splashed oil from being carried into the piston chamber 3 in too great a quantity. and the depending flange 4() of the piston head 12 which continuously overlaps the flange, 16 serves to catch wlmtever oil that passes beyond the rim of the flange 16.

This oil that is trapped by the iiange 40 is deposited at the bottom of the piston chamber 3, and drains therefrom through the,v

i any suitable material, such as regula-r rubber diaphragm stock, or a. good grade of rubber sheet backing which has a strong cloth insertion, maylbe readily placed into the com;

pressor so that it may continue its service.v

To renee 4the diaphragm it is only necessary to remove the bolts 39 and lift ofi` the compressor head 5, and then remove the screw or bolt 44, which r' leases the clamping plate 43. The new diaphragm is then placed in position, clamping plate 43 fastened to the piston head 12, and the compressor head 5 again bolted into position by means of the bolts 39.

The main advantages of my improved compressor lie principally in its simplicity of construction, and its centralized means for lubrication. The one-piece crank case casting and compressor head casting greatly reduces the number of parts and produces an extraordinarily light weight device. The integral connecting rod and piston head further reduces the number of moving parts at the points where lubrication is necessary.

Smce oil is rapidly splashed in the crank case chamber, the shaft bearings 22 and 23, and the bearing surface of the eccentric cam 10 will at all times be provided with sufficient oil to keep them cool and prevent their wearing; and substantially the only part in the entire device that need ever be replaced is the diaphragm 13, which only-requires a few minutes of time to be changed. The valves 30 and 31 in the compressor 5 are readily removable for cleaning, and are. of such simple construction that they may practically never need renewal.

My improved construction is primarily a portable compressor, suitable for use in cases where relatively small quantities of compressed air, at a constant pressure, are required, as in the case of spray guns and the like. The simplicity of its construction permits exceptionally low cost of manufacture. so that the device can be sold as an accessory for spray gun equipment and obviate the necessity1 of investing a large sum in a more complicated device that might not have a sufficient continuity of use to warrant theeX- penditure involved.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that certain details of the construction shown ma be altered or omitted without de arting rom the spirit of this invention as efined by the following claims.

I claim:

1. A diaphragm compressor comprising a crank case' having an upwardly extendin neck, flared outside walls integral on sai neck and terminating in an annular flanged rim, a hollow compressor head having a substantially concave bottom wall and an annular flange reacting with said flanged rim, said compressor head comprising an enclosed plenum chamber and a Walled intake port passing therethrough, said bottom wall hav- -ing apertures leading to said intake port and `said plenum chamber, a check valve in said intake port and in said plenum chamber aperture, a shaft extending into said crank case and journaled thereon, a connecting rod having one end eccentrically journaled on said shaft and an 'upwardly extending free end, a piston head integral on the free end of said connecting rod, an annular collar extending upwardly fro'm the junction of said dared side walls and said neck, annular concentric depending flanges on said piston head, the innermost depending flange surrounding and overlapping said collar and being spaced asl therefrom, a diaphragm clamped between said flanged crank case rim and said compressor head, and a plate clamping said diaphragm concentrically to said piston head.

2. A device of the class described comprising a one-piece crank case terminating in an upwardly extending rim, a compressor head secured to said rim and comprising a plenum chamber having a walled intake port passing' therethrough, an aperture in the bottom of said head communicating with said plenum chamber` a one-way valve in said intake port and aperture respectivelyq a shaft extending into said crank case and journaled thereon,

lan eccentric cam secured to said shaft, a connecting rod iournaled on said cam and having a free end extending upwardly therefrom, a.v piston head on the free end of said connecting rod` overlapping annular flanges on said lil@ piston head and crank caserespectively, a

diaphragm clamped between said rim and compressor head, and means clamping said diaphragm to said piston head.

3. A diaphragm compressor comprising a one-piece crank case terminating at its top in an integral piston chamber having a fianged rim. a flanged compressor head coacting with said flanged rim, said compressor head having an intake port and an enclosed plenum chamber cach communicating with said piston chamber, a valve in said intake port and a valve between said plenum chamber and said piston chamber, a shaft extending into said crank case, a' connectin rod eccentrically journaled on said shaft an having a free end extending upwardly into said piston chamber, a piston head integral on 5 the free end of said connecting rod, a flange extending upwardly from said crank case into said piston chamber and surrounding said connecting rod, a pair of spaced concentric flanges depending from said piston head, the innermost piston flange overla ping said upwardly extending crank case ange and being spaced therefrom, a flexible diaphragm clamped between said com ressor head and the flanged rim of said cran c case, and means clamping said diaphragm to said piston head. Signed at Chicago in the county of Cook and State of Illinois, this 22d day of April,

WILLIAM R. BROWN. 

